Public utilities use large amounts of underground electrical cable, such as electric power cable, telephone and telegraph cable, railroad and other public transportation cable systems, fire and police departments and traffic control signal generation cables and the like.
The preferred place of installation of cables of these type are below ground in conduits which protect the cables from weather and which do not disrupt the environment, either from an aesthetic point of view or from the very real practical problem of supporting many cables on overhead lines. Overhead lines have the further disadvantage of being susceptible to vandalism. In addition, they present potential danger to the population when cable may fall because of accidents, storms and the like.
However, even the best systems ultimately deteriorate. Underground cable either deteriorates and must be removed or replacement may be required of the cable by one which is larger or which contains other features. Even when the cables are placed underground, there is a limit to the number of cables and conduits which can be installed and so, it is desirable to remove old cable.
The process of cable removal can be expensive and difficult, particularly when many cables are packed together and separated by 400 to 800 feet intervals, which is the typical distance between manhole locations, particularly in the city. One device which has been admirably accepted as apparatus for removing cable from underground conduits is shown in U.S. Pat. No. 3,736,822. In this patent, a cable puller is shown which is mounted on a truck and which removes cable from manholes and other underground locations, and thereafter cuts them into disposable lengths. An improvement on that prior patent is disclosed in U.S. Pat. No. 3,799,016, in which an improved puller and an improved cutter are disclosed.
While these devices have served admirably over the past years, industry has been installing larger and more complex cables. As a result, the cables are more difficult to remove and, in some case in large cities, are at a depth which is 10, 20 or even up to 30 feet below the surface of the pavement. Nevertheless, it is important to remove cables once they have been phased out of service.
Not only is there a value in recycling copper, lead and other materials, in some municipalities cables are treated as real estate, resulting in taxation of the value of the installation. Vacant ducts significantly reduce the tax assessment. Thus, even if a cable is no longer in use, until it is removed it remains a source of expense.
One difficulty which has arisen in removing cables from underground locations, particularly as cables are larger and deeper, is that it has become more and more desirable to pull cables in a direction aligned with a true horizontal. If one can envision an 800 foot section of heavily corroded cable packed in a conduit with other cables, one can readily appreciate that tremendous force is necessary to pull the cable out of the conduit.
Efforts to extend the pulling boom into the manhole have not met with success at all. In some instances, the cable access and the boom access are misaligned, even by only as little as two or three degrees. Such a deviation induces a tangential stress moment which causes the cable to rotate in the conduit. The cable, upon rotation in the conduit, either becomes jammed in the conduit and cannot be removed or the cable is subjected to stresses which cause it to rupture or break. In either case, the ability to remove the cable has been frustrated.
Accordingly, it is an object of the present invention to provide apparatus for permitting cable to be withdrawn from conduits in a horizontal direction, thereby optimizing the efficiency of the cable removal apparatus.
Another object of the present invention is to provide a device for use with prior art cable pulling designs while maintaining the self-contained mobility of these truck mounted assemblies.
Still yet another object of the present invention is to provide an extensible mechanism which allows hydraulic movement of a point in both an extension direction and a retraction direction.
Other objects will appear hereinafter.